The present application is directed to electrical power converters, and more particularly to three-phase input to nine-phase output power converters. A variety of electrical power converters have been described in the existing art.
For example, FIGS. 1-3 illustrate various power converter topologies where three-phase power is converted to nine-phase power.
More particularly FIG. 1 illustrates a three-phase input to nine-phase output according to U.S. Pat. No. 5,619,407, which employs a delta connection 100. The nine output voltage vectors have 40° separation from each other. Also depicted in this figure are six non-symmetrical stub type windings which assist in obtaining a desired step down of the voltage. The three-phase power supply is applied at the delta's apexes.
Turning to FIG. 2 a polygon transformer of U.S. Pat. No. 6,335,872 is illustrated 200. This topology employs five windings for each phase. This topology, however, generates undesirable circulating third harmonic current which results in an undesirable increase in the transformer kVA rating. The topology is used for loads which do not require third harmonic currents, and is not considered sufficient for loads presented by a nine-phase AC to DC bridge converter.
Next, U.S. Pat. No. 7,274,280 illustrated in FIG. 3 uses an arrangement of five windings for each phase 300. In this patent the polygon connections are configured so as to reduce the circulating third harmonic current.
In view of the forgoing it is considered useful to provide a new design that provides improvements to the existing topologies, methods and systems.